Author Topic: 375HP OR 425HP ?  (Read 1311 times)

GREEK 1967

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375HP OR 425HP ?
« on: July 17, 2012, 02:50:11 PM »
HAVE A 396 WITH BLOCK #3955272  DATE I-17-68 HEADS ARE 3904391 BOTH ARE DATE I-20-68 4 BOLT BLOCK  6223 CRANK . HOW DO YOU TELL IF 375HP OR 425HP EVERY 375HP I HAVE EVER SEEN HAD 840 HEADS MOTOR WAS IN 69 CAMARO ITS ALL FRESH WITH ROLLER CAM AND 42CC PISTONS   HAD 750 CARB ON DYNO MADE 600HP .

Ed_B

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Re: 375HP OR 425HP ?
« Reply #1 on: July 17, 2012, 03:29:52 PM »
Quote
HAVE A 396 WITH BLOCK #3955272  DATE I-17-68 HEADS ARE 3904391 BOTH ARE DATE I-20-68 4 BOLT BLOCK  6223 CRANK . HOW DO YOU TELL IF 375HP OR 425HP EVERY 375HP I HAVE EVER SEEN HAD 840 HEADS MOTOR WAS IN 69 CAMARO ITS ALL FRESH WITH ROLLER CAM AND 42CC PISTONS   HAD 750 CARB ON DYNO MADE 600HP.

3955272 is a 1969 396 block that was used in applications ranging from 265HP to 375HP. Since yours is a 4 bolt main, it was originally a 375HP configuration. (There were no 425HP 396 engines built in 1969.)

The 3904391 heads are 1967 only, and were used on the Chevelle and Camaro 396/375 engine and the Corvette 427/435 engine. You have a 1969 block and 1967 heads. However, since both your heads are dated I-20-68, it appears they may be service replacements. Can you post a picture of the head dates?

Ed
« Last Edit: July 17, 2012, 07:29:42 PM by Ed Bertrand »

Ed_B

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Re: 375HP OR 425HP ?
« Reply #2 on: July 17, 2012, 06:40:13 PM »
Got the picture John (see below), thanks. I cropped it and rotated it a bit so it could be posted.

The date code is actually I-20-6, so that would be September 20th, 1966, which is correct for the 3904391 heads.

By the way, can you check to see if there's a partial VIN stamped on the block? There should also be a suffix code.

Ed

« Last Edit: July 17, 2012, 07:33:26 PM by Ed Bertrand »

rsr

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Re: 375HP OR 425HP ?
« Reply #3 on: July 22, 2012, 06:31:36 PM »
The 272 block would be a 69 block but it appears you have a 67 model  block that was cast in 1966 if those numbers came from your 4 bolt block with the roller cam making 600 hp??

Ed_B

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Re: 375HP OR 425HP ?
« Reply #4 on: July 22, 2012, 07:34:49 PM »
rsr, you may be getting confused on the casting numbers and date codes.

His block is a 3955272, date coded I-17-68 (September 17th, 1968). His heads are 3904391, date coded I-20-6 (September 20th, 1966). The picture I posted is the one he sent me showing the date code of his heads.

Ed